What are mixed arrays in C#?

Mixed arrays in C# refer to arrays that can store elements of different data types. They were historically used as a combination of multi-dimensional arrays and jagged arrays, but this terminology is largely obsolete in modern C#. Instead, we use object[] arrays or collections to achieve similar functionality.

Note − The traditional "mixed arrays" concept became obsolete after .NET 4.0, as modern C# provides better alternatives like generic collections and tuples.

Syntax

Following is the syntax for creating an array that can hold mixed data types −

object[] arrayName = new object[] { value1, value2, value3 };

Following is the syntax for using Tuple as an alternative −

Tuple<type1, type2> tupleName = new Tuple<type1, type2>(value1, value2);

Using Object Arrays for Mixed Data Types

An object[] array can store elements of any type since all types in C# inherit from the object class −

Example

using System;
using System.Collections.Generic;

class Program {
   static void Main() {
      object[] mixedArray = new object[] {89, 45, "jacob", 9.8};
      
      Console.WriteLine("Mixed Array Elements:");
      for(int i = 0; i < mixedArray.Length; i++) {
         Console.WriteLine($"Element {i}: {mixedArray[i]} (Type: {mixedArray[i].GetType().Name})");
      }
   }
}

The output of the above code is −

Mixed Array Elements:
Element 0: 89 (Type: Int32)
Element 1: 45 (Type: Int32)
Element 2: jacob (Type: String)
Element 3: 9.8 (Type: Double)

Complex Mixed Arrays with Collections

You can also include collections and other complex objects in mixed arrays −

Example

using System;
using System.Collections.Generic;

class Program {
   static void Main() {
      var complexArray = new object[] {
         87, 
         33, 
         "tim", 
         6.7, 
         new List<string>() {"football", "tennis", "squash", "cricket"}
      };
      
      Console.WriteLine("Complex Mixed Array:");
      foreach(var item in complexArray) {
         if(item is List<string> list) {
            Console.WriteLine($"List: [{string.Join(", ", list)}]");
         } else {
            Console.WriteLine($"Value: {item} (Type: {item.GetType().Name})");
         }
      }
   }
}

The output of the above code is −

Complex Mixed Array:
Value: 87 (Type: Int32)
Value: 33 (Type: Int32)
Value: tim (Type: String)
Value: 6.7 (Type: Double)
List: [football, tennis, squash, cricket]

Modern Alternatives: Using Tuples

For structured mixed data, tuples provide a better alternative than mixed arrays −

Example

using System;

class Program {
   static void Main() {
      Tuple<int, string> tuple = new Tuple<int, string>(60, "John");
      
      Console.WriteLine($"ID: {tuple.Item1}");
      Console.WriteLine($"Name: {tuple.Item2}");
      
      // Using ValueTuple (C# 7.0+) - more concise syntax
      var person = (Id: 99, Name: "Jack");
      Console.WriteLine($"Person ID: {person.Id}, Name: {person.Name}");
   }
}

The output of the above code is −

ID: 60
Name: John
Person ID: 99, Name: Jack

Comparison of Approaches

Conclusion

While mixed arrays using object[] allow storing different data types in a single array, modern C# favors type-safe alternatives like tuples and generic collections. Use object[] only when you truly need dynamic typing, and prefer tuples or strongly-typed collections for better performance and maintainability.